INTRODUCTION TO HELICOPTER FLYING

Transcription

1 r_helicopter Operations Manual* 7/7/03 4:19 PM Page 2 INTRODUCTION TO HELICOPTER FLYING Flying a helicopter may be a completely new experience for you and we want to ensure that we maximise your enjoyment. To this end we have secured the valuable expertise of Hover Control - a virtual helicopter flying and on-line training group. We have some valuable information below that has been lifted directly from their website to get you started and you can find out much more by visiting their website How a helicopter flies We are going to skip all of the clichés and analogies often used to describe how a helicopter flies, or how they behave in relation to fixed wing counterparts. We will start by saying that Helicopters are undoubtedly the most complex flying machines ever created...period. Helicopters have amazing and unique flying capabilities, but they come at a price of mechanical complexity, fuel inefficiency, reliability, and maintainability. It is best when learning how a helicopter flies, to treat the helicopter as a unique flying machine, and NOT as a derivative of the fixed wing aircraft. After understanding some of the basic principles behind helicopter flight, you'll hopefully have a new appreciation for how these wonderful machines work. Yaw, Pitch, and Roll Hopefully you are already familiar with these three axis of flight, if not here is a refresher. Pretend your head is an helicopter and do the following: 1. Keeping your head level, look right, then look left. That's yaw. 2. Look up at the ceiling, then look down at the floor. That's pitch. 3. While looking forward, cock your head to the left, and then to the right. That's roll. Main rotor disc, and thrust. When the main rotor is spinning it creates what is referred to as a "rotor disc", when the blades are set at a position to bite into the air (like a fan) using a flight control called the "collective", this rotor disc begins to create thrust. This thrust travels in a direction that is perpendicular to the rotor disc (so does the main rotor shaft). If the helicopter is sitting level on the ground, and the rotor disc is also level, the thrust is being directed straight down. If the blades where to bite into the air enough, the amount of thrust being produced would overcome the weight of the aircraft, and the helicopter would begin to lift off, straight up. What type of controllers/joystick should I use for Helicopters? For in depth advice for what controllers are best we suggest you ask our members by posting a message in the "General Discussion Forum". However, as a basic rule you will need a good joystick 2

2 r_helicopter Operations Manual* 7/7/03 4:19 PM Page 3 with as many programmable buttons as possible, a smooth easy to operate throttle slider, and a twist grip stick for rudder control. If you can afford separate pedals, that is highly recommended. Force Feed Back joysticks don't tend to get great reviews from the helicopter community, so you may want to ask around before committing to one. What Realism settings should I use for flying with Hovercontrol and Training? If you have just started flying helicopters we suggest setting your realism sliders all to about half way. Once you have begun flying well you will most likely want to move your realism sliders closer to 100%, 99% (or one notch from 100%) tends to be a popular setting among helicopter simmers here. However, you can experiment for yourself because it will depend on what helicopter you fly most. We also suggest that you don't use "Unlimited Fuel" and that you have "Detect Crash" turned ON, Aircraft Collisions turned OFF, and Aircraft Stress causes Damage turned On. These settings will help you make your flights more realistic, which will help you take things more seriously. Directing Main Rotor Thrust Now that we can visualise the main rotor disc producing thrust in a straight downward direction, we can tilt the rotor disc (the helicopter will follow) in order to convert some of that upward force (produced by downward thrust) into forward force. The more we tilt the disc forward, the more forward force we will gain, and the less thrust will be available to force the helicopter upward. The helicopter will gain speed forward, but will begin to lose altitude. To counteract the drop in altitude, we will either have to level the rotor disc once again, or increase the overall power and bite of the blades. It is important to understand that this thrust can be directed in any direction (forward, rear, left, or right) using the flight control called the "cyclic" or the "stick", so that increasing velocity in any direction becomes possible. Not necessarily safe, but possible. Tail Rotor, Anti-torque As the main rotor spins, it causes the rest of the helicopter (connected to the rotor disc by the main rotor shaft) to spin with an equal amount of force in the opposite direction. To counter-act this force, the tail rotor produces thrust that pushes against the helicopters spinning motion. The amount of thrust produced by the tail rotor is controlled by use of the anti-torque pedals at the pilot's feet. In a hover, or at low speeds, the pilot can use controlled variations in the tail rotor thrust to spin the helicopter right or left on the yaw axis. 3

3 r_helicopter Operations Manual* 7/7/03 4:19 PM Page 4 Full Forward Flight As the helicopter gains forward velocity, air moving over the vertical stabiliser at the rear of the aircraft will begin to increase its effectiveness. Eventually the use of the anti-torque pedals in order to keep the helicopter aligned to a particular heading will be unnecessary. The helicopter does not have a controllable rudder, instead turns at high speeds are performed using a co-ordinated amount of roll and pitch. The Cyclic "The Stick" The cyclic is named after its purpose, that is to provide control input to the spinning main rotor blades during their cycle through 360 degrees of rotation. When the pilot pushes the cyclic stick to the right, the mechanics of the rotor control system cause the blades to bite more into the air as they travel around the left side of the helicopter and bite less as they travel around the right side of the helicopter. This causes the left side to rise and the right side to sink, beginning a roll to the right...and yes...this happens on every single rotation (or cycle) of the rotor blades! The Collective The collective is also named after its purpose, to provide control input to the main rotor blades during their entire rotation. It does this by "collectively" effecting all of the rotor blades during the entire rotation. If all blades are collectively increased in pitch during their entire rotation, the result will be increased thrust being produced by all of the blades equally. Co-ordinating the Controls The complexity of helicopter flight comes from the fact that the collective, cyclic, and anti-torque pedals are manipulated independently but in a constant and co-ordinated fashion by the pilot in order to get the helicopter to move where he or she chooses. There is no way to just set the controls where you want, and sit back to enjoy the ride. Instead, flying a helicopter is more like treading water in a deep pool, your arms and legs (if you use pedals) constantly making small adjustments to the controls to account for wind drift, gravity, and thrust. Translational Lift and Ground Effect As a helicopter lifts off the ground into a stationary hover, its main rotor blades have to work extra hard to produce thrust, because the air they are turning through is turbulent due to the blades themselves. Translational lift occurs as the helicopter begins to move forward and begins transitioning to forward flight (around 40kts), the blades begin hitting smooth undisturbed air and start to produce more thrust. A slight "bucking" occurs as the front of the spinning rotor disc creates more thrust than 4

4 r_helicopter Operations Manual* 7/7/03 4:19 PM Page 5 the rear. Ground effect occurs when the rotor disc is producing thrust in the direction of a hard smooth surface such as a paved helipad. Because the thrust hits against a hard surface, it is more effective than if the thrust is hitting nothing or a soft surface such as long grass. Helicopter Limitations The most notable limitations that helicopters face is max cruising speed and useful range. High cruising speeds are impossible for helicopters due to the fact that as the main rotor blade spins it is affected by disymmetry of lift. Disymmetry of lift simply means that as the helicopter moves forward at high speeds, the forward moving blade gets more and more lift, while the blade travelling toward the rear of the aircraft gets less and less. This has been partially countered in newer helicopter designs by allowing the rotor blades to flex vertically as needed, however for most helicopters it still limits their max cruising speeds to the less than 200kts. Useful range is also a challenging factor in all helicopter designs. Because helicopters require so much power to lift, their fuel payload and consumption rates are major design considerations. Because the power to weight ratio of a helicopter design is so crucial, and fuel is so heavy, their ranges are often limited compared to fixed wing aircraft. Sim vs. Reality, What to expect If you are using FS2002, you'll be training using what is probably the most advanced consumeravailable simulation software. However there are some limitations to simulation, especially in regards to helicopter flight, that you should be aware of before reaching flight school. When you hear new flyers stating that the helicopter in MSFS can't be flown, it is usually because they have the wrong type of controls, or they have not learned to overcome one or more of the following factors: Lack of physical sensations You won't be able to feel small changes in motion. You also won't be able to sense your speed or altitude as clearly as you would in real flight. When it comes to helicopters, these sensations are very important, especially at lower speeds and altitudes. Without these physical cues, our situational awareness will be challenged. It will place greater importance on the few cues the simulator does provide, and the instruments that tell us things our bodies can't feel. Lack of peripheral vision Yes there are virtual cockpits with point-of-view joystick controls. There are also multiple views that can be used within the 2d-cockpit mode. However, these can't come close to the real life ability to take a quick look out of the corners of your eye. This means most of the time, you'll be getting your visual cues from the forward view of the 2d or virtual cockpit. Surprisingly, with a little practice and experience, you'll find the simulator will give you quite a lot of information about the situation of your aircraft in this view. The cues are small, but can be used effectively once you begin to recognise them. 5

5 r_helicopter Operations Manual* 7/7/03 4:19 PM Page 6 Sterile Controls Slow to Respond Even with the highest sensitivity settings, and realism settings, the controls you use will most likely not create the type of response in the helicopter that you would expect in a real helicopter. Your controls will most likely also not give you the hydraulic feed back and sensation that real controls would. In general the flight simulator software is sluggish when it comes to fine control inputs. This is a limitation that is not soon to be fixed, as there are literally hundreds of pieces of information that have to be updated each time the simulation software detects control input. Those are the limitations. However, there are also some advantages to simulation that can make your training and flight experiences more enriching. The Pause Button Some people think the pause button is the most unrealistic aspect of simulation. Despite this, it remains a powerful tool in your flight experience. It allows you the time to take a second look at the tasks at hand. Some times a quick pause is all you need to get your wits back, and correct that out of control hover before crashing. It might be unrealistic, but it is simulation, and it can be a powerful tool. Instant Replays I think all pilots would like to have a 24x7 cameraman to document every aspect of their training. Well with MSFS you can easily take a second look at the great landing you just did, and the bad landing too! External Views One thing real pilots will never have is the ability to step outside of their aircraft and take a look at their flying from the external perspective. Some simulation buffs discount this as unrealistic, but in training, you might find it incredibly important. Any new pilots with previous experience with remote controlled aircraft will definitely appreciate spending a little stick time while viewing the aircraft from the 3rd person. You might find that an occasional look from the outside will help boost the realism of your flight because it will help your brain see that the aircraft you are flying really exists in the simulated world. Total Environment/Situation Control You will have the power to change lighting conditions, weather, and seasons. This will give you great flexibility in your training and flight operations. This is undoubtedly one of the most powerful tools 6

6 r_helicopter Operations Manual* 7/7/03 4:19 PM Page 7 offered by simulation software, in fact it is this ability that makes simulation so important during real life training programs. Acknowledgements We extend our grateful thanks to everyone at Hover control without whom this valuable introduction would not have been possible. Of course not forgetting our own technical expert John Bulteel for finding the most valuable points to get you started. And last but not least to Arnie Lee and the team at Abacus without whom we wouldn't have any Helicopter Operations to fly. 7